Organic interdispersion cold bonding control agents for use in mechanical alloying

ABSTRACT

The invention involves mechanical alloying of powder wherein the formation of composite powder particles characteristic of the mechanical alloying process is facilitated through the use of special organic interdispersion cold bonding agents, e.g., stearic acid. The invention is particularly applicable to the production of non-dispersion hardening superalloys.

United States Patent 1 Volin [451 Apr. 15, 1975 ORGANIC INTERDISPERSION COLD BONDING CONTROL AGENTS FOR USE IN MECHANICAL ALLOYING [75] Inventor: Timothy Earl Volin, Tuxedo, N.Y.

[73] Assignee: The International Nickel Company,

Inc., New York, NY.

[22] Filed: Jan. 29, 1973 [21] Appl. No.: 327,321

[52] US. Cl 75/0.5 R; 75/.5 AB; 75/.5 BA; 75/211; 75/171 [51] Int. Cl B22f 9/00 [58] Field of Search 75/.5 R, 214, 211, 171; 241/15; 264/111 [56] References Cited UNITED STATES PATENTS 8/1961 West et a1 18/48 1/1967 Lonquist et a1.... 11/1969 Lambert et al. 75/206 3,740,210 6/1973 Bomford et a1. 75/.5 AC

OTHER PUBLICATIONS The Role of Additives in Milling, A Treatise on the Internal Mechanisms of Ball, Tube and Rod Mills, H.E. Rose and R.M.E. Sullivan, 1958, pp. 236251.

Primary ExaminerL. Dewayne Rutledge Assistant Examiner-Arthur .l. Steiner Attorney, Agent, or FirmEwan C. MacQueen; Raymond .1. Kenny 5 7 ABSTRACT 2 Claims, N0 Drawings ORGANIC INTERDISPERSION COLD BONDING CONTROL AGENTS FOR USE IN MECHANICAL ALLOYING The present invention relates to powder metallurgy. and is particularly directed to the "mechanical alloying" of powder.

As is known. the recently introduced concept of mechanical alloying, described in U.S. Pat. No. 3.591.362 (incorporated herein by reference). involves a dry. intensive milling of powders in high energy machines. such as the Szegvari attritor. During this unique process. initial constituent powders are repeatedly fragmented and cold bonded by the continuous impacting action of attriting elements. usually metal balls. for a period such that composite product powder particles of substantial saturation hardness are formed. the composition of which correspond to the percentages of the respective constituents in the original charge. The constituent powders become most intimately interdispersed at close interparticle spacings. the composite particles being exceptionally dense and homogeneous. and characterized by cohesive internal structures.

For the most part mechanical alloying" (often herein MA) has been conducted in the presence of an atmosphere comprised of an oxygen-nitrogen mixture. However, such an environment can serve to introduce various problems. particularly in respect of nondispersion strengthened alloys of the superalloy type. For example. oxygen is retained in the composite product particles formed. As a consequence and depending upon the alloy composition to be produced. this can subvert certain metallurgical properties. tensile and creep ductility of nickel-base superalloys being illustrative. Moreover. if present to the excess. comminution of the powders dominates to such an extent as to virtually preclude the critically necessary cold bonding.

On the other hand, in the absence of such atmospheres the powders either adhere irreversibly to the attriting elements and interior attritor surfaces (with subsequent buildup) or. depending upon the composition of the attriting elements and powder charge, may irreversibly cold bond to form undesirably large particles. In the former case the layer bonded to the balls, and in the latter case the large particles. are too thick to be satisfactorily deformed by the energy available in subsequent collision events. Processing therefore effectively ceases. Indeed. a point may be reached where there is such an overload on the attritor as to bring about a self-induced shut-down. This. quite naturally, leads to considerable loss occasioned by down-time. In any case, powder recovery is extremely poor.

It is evident from the foregoing that an indispensibly necessary mechanical a loying control balance" must be achieved, this control balance" being defined as one in which the intimate interdispersion of constituent steady state processsing (fragmentation and cold bonding reaching a virtual equilibrium), but (i) without incurring serious impairment of the metallurgical properties of the alloy to be produced due, for example, to excessive oxygen retention in non-dispersion strengthened alloys, (ii) without the formation of appreciable quantities of detrimentally large composite product particles, and (iii) without the deleterious adherence of powders to the attriting (milling) elements or other attritor surfaces.

.powders continues by means of the establishment of A [t has now been discovered that the above drawbacks can be considerably minimized. if not virtually eliminated. that the desired control balance" can be attained. through incorporating an effective percentage of at least one interdispersion. cold-bonding agent (lCBCA). as herein detailed.

Generally speaking. it has been found that an organic agent. including organometallic compounds. capable of reacting with or of being adsorbed on a plurality of the powder (particle) surfaces of an initial powder charge and which is capable of residing thereof in reacted or adsorbed form during at least a significant part of the mechanically alloying process. is effective in achieving the aforedescribed control balance". (Such materials include organic compounds which decompose such as to form a constituent capable of reacting with or of being adsorbed on the powder surfaces.) Only a small quantity of the organic lCBCA is required. though this is dependent upon the given conditions used in producing the desired mechanically alloyed composite product powder particles as is further described herein.

In accordance herewith. lCBCAs such as the following are contemplated: saturated hydrocarbons such as methane. ethane. propane and hexane; unsaturated hydrocarbons such as ethylene. allene. hexene and acetylene; alcohols. including methanol. ethanol. and ethylene glycol; aldehydes. e.g.. formadehyde. trioxane. acetytaldehyde. and benzaldehyde; ethers. for example. methyl or vinyl ether; ketones. such as acetone; polymers of the foregoing; organohalogen compounds. including the carbon tetrahalides such as (TF and polymers thereof such as polytetrafluoroethylene: organometallic compounds. for example. nickel or cobalt stearate. triethylaluminum, dicyclopentadiene-nickel. nickel tetracarbonyl'. fats and fatty acids such as stearic acid, stearin, and the formic, oleic. and oxalic acids: etc. (This listing is not intended to be exhaustive.) lt is considered that such materials by virtue of their reacting with or being adsorbed on the surfaces of the powder particles are occluded during collisional events between powder particles and this inhibits metal-to-metal bonding. This largely contributes to the desired "control balance.

The amount of an lCBCA employed will be largely influenced, inter alia. by the alloy composition to be produced, milling time, machine design and speed. ball-to-powder ratio, and the nature of the attriting elements, particularly the latter. Hardened steels. stainless steels, tungsten carbide, nickel and other metals as well as cermets may be used as the attriting media; however, considerably less ICBCA will usually be necessary in conjunction with the harder attriting elements such as 52,100 steel as opposed to, say. nickel. The longer milling periods may require a slightly higher percentage of lCBCA than otherwise. Generally. not more than 2 or 3 percent of an effective lCBCA component need be employed, a range of 0.05 or 0.1 to 0.5 percent and up to 2 percent being deemed satisfactory. Excessive amounts can be detrimental. In terms of a hydrocarbon such as. for example, acetylene, about 0.025 to 2 percent carbon as hydrocarbon can be used. with 0.05 to 0.5 percent being considered advantageous.

Due to the high energy milling of mechanical alloying. a part of the attriting composition may wear during processing and become a part of the composite product particles. This can be beneficial but if undesirable. re-

course should be had to a more appropriate attriting composition.

It is perhaps worthy of mention that not all of the lCBCA can be removed and this does focus attention ered that the recovery for the polytetrafluoroethylene (PTFE) of Run No. 5 would be improved using steel balls as the attriting elements.

The present invention is particularly applicable to the on a major difference between the subject invention 5 production of non-dispersion hardening superalloys inand conventional ball miling in which surfactants. lueluding those containing up to 65 percent, e.g., from 2 bricants and other grinding aids are used for various percent up to 25 or 35 percent, chromium; up to 30 purposes. mainly for powder comminution. Generally. percent, e.g., 5 to 25 percent, cobalt; up to percent, the latter are virtually completely removed from the 1 t 9 percent l i d up to 3 percent powder by expedients such as leaching or burning off. 10 1 m 7 percent i i i l di those ll In Contrast due to the necessur) intimate interdlspflcontaining 4 or 5 percent or more of aluminum plus tision of constituent powders which occurs by reason of i up to 30 percenh Kg" 1 to 8 Percent l bd mechanical alloying. removal techniques affecting up to 25 percent 6g, 2 to percent tungsten; only the composite particle powder surfaces are incaup w 1() percent 1 bi up to 10 percent m pable of extricating all the lCBCA since an amount of 15 up to 7 percent Zirconiurm up to 0 5 percent b it is occluded in interdispersion fashion. ron, up to 5 percent hafnium, up to 2 percent vana- The fOllO\Vlng illustrative data are given: dium up to 6 percent copper up [0 5 percent munga. EXAMPLE nese, up to 70 percent iron, up to 4 percent silicon. and the balance essentially nickel. Cobalt-base alloys of Composite product powder particles of the alloy 30 similar composition can be treated. Among the specific known as lN-792 were produced using various lCBCAs superalloys might be listed lN738, Rene alloys 41 and and either nickel or steel attriting elements. Powder 95, Alloys 500, 700. 713 and 718, Waspaloy, Astroloy. blends were used. each being comprised of carbonyl Mar-M alloys 200 and 246, A-286, B-l900, etc. Hownickel powder (99.l percent nickel approximately 4 ever, such superalloys and other contemplated alloys microns in size), 0.15 percent Asbury flake graphite to can also contain up to. say, 10 percent by volume of a raise the carbon content to nominal, and a low oxygen refractory dispersoid material including the oxides, caromnibus master alloy (-lOO mesh of percent Ni, Cr. bides, nitrides and borides. Such refractory dispersoids Mo, Co. Al, Ti. W, Ta, B. Zr and C) prepared by vaccan be of various elements including yttrium, lanthauum induction melting and grinding in cold nitrogen. num, thorium. zirconium, hafnium, titanium, silicon, Each run consisted of 5 grams of the blended powder 30 alluminum, cerium, uranium. magnesium, calcium, beplus the particular lCBCA used as given in Table l. ryllium and the like. As a practical matter, only a very A Spex mill was employed in each case, the respeC- small amount of such dispersoids need be employed, tive runs being conducted for 30 minutes under an e.g., up to 2 percent by volume. Other base alloys such argon atmosphere (atmosphere was acetylene plus as titanium and copper can be processed as well as reargon in Run No. 6). The Spex milljar was cooled prior fractory alloys such as SU-l6, TZM, Zircal y, etc, to opening. emptied and the balls replaced in the jar Finally, it will be understood that modifications and and processed for an additional 30 seconds in air to revariations of the invention may be resorted to without move any loosely adherent powder. The total amount departing from the spirit and scope thereof as those of drained powder was weighed to ascertain the perskilled in the art will readily understand. Such are concemage of Powdt?r recm'ered- Oxygen analysis W115 40 sidered to be within the purview and scope of the inalso made. and retained lCBCA was determined for vention d d d l i Runs. Nos. 4 and 6. Nos. 1 and 2 are included for purl i poses of comparison. 1. in the process of producing mechanically alloyed TABLE I Attriting Powder Oxygen Run ICBCA Element Recovery Analysis ICBCA i (9i Retained l None Nickcl( 100 gm) 32 0.30 2 None Steel 100 gm) 57 0.17 3 Stcaric Nickel( I00 gm) Xl 0.46

Acid. W 4 Stcaric Stccl 100 gm) 81 0.22 0.329 C Acid, 0 l6? 5 P'El- E Nickelt I00 gm) 65 0.3] 6 A c c iv Slccl 100 gm) vs 0.21 0.290; c

lcnc

atmosphere estimated to be about It); Acetylene The low recovery of Run. Nov 1 reflects the detri- 60 superalloy composite product powder particles consistmental adherence of the lN-792 powder to the milling elements and to the interior surfaces of the mill. This was reduced somewhat by using the harder steel impacting elements in Run No. 2. Runs 3 and 4 further illustrate the marked effect of the nature of the attriting elements, only one-tenth of the stearic acid lCBCA being required with steel balls to give the same recovery attained using the softer nickel pellets. lt is considing of up to percent chromium, up to 10 percent alluminum, up to 8 percent titanium, up to 30 percent molybdenum, up to 25 percent tungsten. up to 10 percent columbium, up to 10 percent tantalum, up to 7 percent zirconium, up to 0.5 percent boron, up to 5 percent hafnium. up to 2 percent vanadium, up to 6 percent copper, up to 5 percent manganese, up to percent iron, and the balance essentially nickel and/or such that an intimate interdispersion of constituent powders is achieved without incurring serious impairment of the mechanical properties of the composition to be produced and without either the formation of an appreciable amount of detrimentally large composite particles or the deleterious adherence of powders to the milling elements or mill interior surfaces 2. A process as set forth in claim 1 in which the lCBCA is methane present in an amount from 0.1 to

0.5 percent by weight of the powder charge. 

1. IN THE PROCESS OF PRODUCING MECHANICALLY ALLOYED SUPERALLOY COMPOSITE PRODUCT POWDER PARTICLES CONSISTING OF UP TO 65 PERCENT CHROMIUM, UP TO 10 PERCENT ALLUMINUM, UP TO 8 PERCENT TITANIUM, UP TO 30 PERCENT MOLYBDENUM, UP TO 25 PERCENT TUNGSTEN, UP TO 10 PERCENT COLUMBIUM, UP TO 10 PERCENT TANTALUM, UP TO 7 PERCENT ZIRCONIUM, UP TO 0.5 PERCENT BORON, UP TO 5 PERCENT HAFNIUM, UP TO 2 PERCENT VANADIUM, UP TO 6 PERCENT COPPER, UP TO 5 PERCENT MANGANESE, UP TO 70 PERCENT IRON, AND THE BALANCE ESSENTIALLY NICKEL AND/OR COBALT, THE IMPROVEMENT WHICH COMPRISES CONDUCTING THE MECHANICAL ALLOYING OPERATION IN THE PRESENCE OF AN INTERDISPERSION COLD BONDING AGENT (ICBCA) SELECTED FROM THE GROUP CONSISTING OF METHANE, ETHANE, PROPANE AND HEXANE, THE ICBCA BEING IN CONTACT WITH THE POWDER PARTICLES TO BE MECHANICALLY ALLOYED AND BEING PRESENT IN AN AMOUNT EFFECTIVE TO PROVIDE THE NECESSARY CONTROL BALANCE DURING THE COURSE OF THE OPERATION WITH THE UPPER LIMIT BEING NOT GREATER THAN 3 PERCENT BY WEIGHT OF THE POWDER CHARGE, THE CONTROL BALANCE BEING SUCH THAT AN INTIMATE INTERDISPERSION OF CONSTITUENT POWDERS IS ACHIEVED WITHOUT INCURRING SERIOUS IMPAIRMENT OF THE MECHANICAL PROPERTIES OF THE COMPOSITION TO BE PRODUCED AND WITHOUT EITHER THE FORMATION OF AN APPRECIABLE AMOUNT OF DETRIMENTALLY LARGE COMPOSITE PARTICLES OR THE DELETERIOUS ADHERENCE OF POWDERS TO THE MILLING ELEMENTS OR MILL INTERIOR SURFACES.
 2. A process as set forth in claim 1 in which the ICBCA is methane present in an amount from 0.1 to 0.5 percent by weight of the powder charge. 